Poison Sacs (3.5e Feat)

From D&D Wiki

Benefit: When you gain this ability choose any poison in Dungeons and Dragons with a DC equal or less to the DC your poison would have (10 + 0.5½ HD + Con mod). You poison does ability damage or special effects equal to the poison chosen.
Once chosen, your poison type does not change, but your poison DC will increase when your HD or Con modifier increase.